Layer 2 Virtual Private Network (L2VPN) and Virtual Private Local Area Network Service (VPLS) services allow customer sites that are geographically dispersed to share an Ethernet broadcast domain by connecting the sites through pseudo wires, which emulate the transaction of a “wire” connecting the customer sites. These pseudo wires are commonly known as Virtual Leased Lines (VLLs). Under the pseudo wire end to end emulation (PWE3) model, a customer uses native format (i.e., original traffic type) attachment circuits to connect to a service provider's provider edge (PE) routers. To transport data from one customer site to another over a Multiprotocol Label Switched (MPLS) network, a MPLS Label Switched Path (LSP) transport path is established between the PE routers using the Resource Reservation Protocol-Traffic Engineering (RSVP-TE) protocol or Label Distribution Protocol (LDP) protocol. These MPLS LSPs, however, are transparent to the customer. From the customer's perspective, the pseudo wire acts as a wire connecting the customer's sites, and traffic is exchanged between the sites using the customer's native/original traffic type.
To achieve resiliency of VLL services, more than one pseudo wire (typically, two) are configured to provide redundancy of L2VPN/VPLS services. Among the redundant pseudo wires, only one pseudo wire will be active and all other redundant pseudo wires are in standby state. The MPLS transport path used by these redundant pseudo wires, however, could share one or more same physical links between the PE routers. In cases where redundant pseudo wires do share one or more same physical link, the redundant pseudo wires could share the same fate or risk of failure. In other words, if there is a failure in one of these shared links, the result will be a total loss of the VLL services, even though redundant pseudo wires have been established for the VLL services.